Problems troubleshooting low voltage at starter solenoid - Page 4 - PeachParts Mercedes-Benz Forum

RAYMOND485 · #1 07-01-2010, 09:18 PM

1984 300D TURBO 152K
INSTALL A RED TOP 34 REV. OPTIMA BATTERY, WILL FIT, MOUNTS AT BOTTOM
COST 2X,NO LEAK, SHIP TO HOUSE, FREE SHIPPING , USE LONG GROUND CABLE AND GOOD POWER

vstech · #2 07-03-2010, 08:19 PM

1.1 volts is nothing during start.
unless you are below 12.6v to begin with.
if you are below 12.6 with everything off, your battery is low or bad.

nealpellecchia · #3 05-05-2013, 07:24 PM

Quote:

Originally Posted by HinuWahie

Sorry for the saga... I have an ongoing problem with my starter that has me confused and unsure of my next move.

I have had my '83 300sd (with 265k) for 4 years now, and it was trouble free for the first 3 1/2. Right after I bought it, I transfered SVO from my previous sd and it has really been the worry free daily driver we all expect from our diesels.

About 6 months ago I started having starter troubles. In retrospect, they were the classic signs of an old starter, eg slower cranking, intermittant no cranking, occational non responsiveness when warm etc. After ignoring the problem one weekend too many, it left me stranded at work on a friday night . Needing to get to work monday, I bought a starter at the only place that had one, Shucks (no rocks please...). The first one had a problem with the contact plate welding itself in on position, the second had stripped threads. The third one lasted for about 5 months, but had had a few intermitant problems with the contact plate, and just seemed weak. I tried bypassing the NSS and ignition by jumping the leads at the terminal block, but got nothing from the starter, just a clicking that came from the glow plug relay. Upon removal the solenoid was unresponsive, though starter motor would spin if I bypassed solenoid.

It was at this point I thought something was going on with the car and not the cheap starters. reading the posts here, I convinced myself its was the ignition switch causing problems, so it was replaced. Starter 4 came from Napa, but only lasted 2 weeks. This one also had an unresponsive solenoid. Again I had tired jumping the terminal leads, just the click at the glow plug relay. From what I gather here, this may be normal, as the relay was set up stop energizing the glow plugs on start...

I'm on starter 5 and tying to get to root cause before I take another one out.

Someone at work was telling me low voltage at the solenoid would cause it to fail prematurely (the low voltage allowing the solenoid to activate, but at a higher current draw, causing heat...).

Sure enough, at the connection on the solenoid I get 10.5 V to ground (at the battery). Thinking it may be the ground straps, I ran a jumper cable from the starter housing to the neg battery post; same result.

Working my way back, I disconected the white solenoid lead (shown with with green arrow) at the termimal strip, left it unconnected and checked starting voltage up to its signal lead (connector with two purple leads, one about 10-12 ga, and one 14-16 ga, shown with red arrow). 11.2 V on start. So I'm losing ~.7V in the wire to the solenoid, but where is the rest going?

The ignition switch is new, so maybe NSS? Tried locating the connector, above the acc pedal, under carpet to right of acc pedal, no luck... So I pulled the NSS connector on the tranny. It was a little oily, but not corroded. I cleaned the leads, reconnected and tested. Still 11.2V. I also noticed the igntion signal lead (still measured at purple leads at terminal strip) was giving low voltage signals during glow (1.3V), prior to start (2.6V right after a click from somewhere, 5-6 sec after glow light turned off), after "start" .2V, and even when key goes back to "0" position of -.2 V! (going back to verify this -.2V, it seems to drop off over a few minute period; like a capacitor discharging)

Unsure about what to do next, and thinking about the glow plug clicking from before, I pulled the likely connector that contains the link from terminal strip to glow plug relay, and retested voltage during start. 12.3 V.

The low voltage signals seemed to be reduced with connector removed, to .2 V prior to start (of course there s no "glow" light with the connector removed).

At this point I'm thinking the glow plug relay/timer is bad, but thats just cause it seems like it acting funny, actually drawing power from starter signal (but they're in parrallel,right??), not because i understand the problem. Before I drop 100+ (plus install time I dont really have)on a new relay kit, I was hoping someone here may have an insight as to what the cause of the voltage drop might be.

Or should I even worry about it. I was considering installing a low voltage starter relay (like the Bosch WR-1 kit), just to make sure the solenoid sees 12V. That may be masking a future problem with the glow plug relay, I just dont know.

Thanks in advance for your help/advice.

The solenoid should pull in and work at like 9.5 volts or so because often you get low voltage through a cars life span. my first gm starter never failed despite low old batteries etc. It lasted 15 years.

I have the same problem as you! It's a 1993 chevy turbo diesel. My chinese rebuild was suppose to be new. It has been a problem with noise from the beginning. I have my "giggle wire" attached to the solenoid switch terminal because I knew the problem would act up again and I don't feel like taking it out again like you. After 3mos. he gave me a new solenoid. that stopped working after another 4mos. I used a screwdriver for many mos. cause I didn't want him to have to take it out again. Finally I got another guy to open up the solenoid and look at the contacts. He immediately saw a very thin contact washer and replaced it with a much thicker new one I hope. It was good for 4 days. Out again and back to the original guy and he replaced the cap with it's new contacts. I thought great we got to the heart of the problem; good for 4-5 days. Hence my giggle wire.

This is how it works. It's a pretty thick wire well attached to the solenoid S terminal and it hangs loose near the battery. When the key won't start it and it will "click" but not start, I pull out the wire and at first it will start by just touching the wire to the + post.More amps I presume. But often this won't work and I have to scratch, scrape, or giggle the wire on to the post so it will giggle the solenoid contacts enough to make a connection. This never failed until yesterday. And it was hot ...no glow plug voltage used. I had to leave the hood up and perhaps cool the engine and lower the resistance in the wires and then it started. I need to put a gauge right on the starter motor wire and see how much current I am getting across the solenoid contacts to the starter motor when it fails. If it's normal then I'll have to see where it's grounding-shorting out or where the current stops at a bad ground. I think.